Rigorous analysis on performance of LEO satellite ground station in urban environment

Microsatellites in low Earth orbits (LEOs) have been in use for the past two decades. LEO satellites are used for public communication and also for scientific purposes, and the orbits vary with the type of satellites and the primary purposes. LEO scientific satellites have a variety of applications, including Earth surveillance and astronomy applications. These satellites provide opportunities for investigations for which alternative techniques are either difficult or impossible to apply. Thus, it may be expected that such missions will be further developed in the near future especially in fields where similar experiments by purely Earth‐based means are impracticable. Ground stations have to be established in order to communicate with such satellites, and the quality of communication depends on the performance of the satellite ground station, in addition to that of the satellite. Before the implementation of the ground station, analyses related to environmental factors have to be considered, especially in urban areas. Rain effects, the impact of intermodulation products, and contact time duration at low elevation angles are some of the aspects that are considered in this work and which influence the final decisions on the design of the ground station. Measurements on the ground station based on Sun flux density are described, which provide an opportunity to check the performance of the ground station. Copyright © 2007 John Wiley & Sons, Ltd.     

Performance Evaluation and Policy Selection in Multiclass Networks

This paper concerns modeling and policy synthesis for regulation of multiclass queueing networks. A 2-parameter network model is introduced to allow independent modeling of variability and mean processing-rates, while maintaining simplicity of the model. Policy synthesis is based on consideration of more tractable workload models, and then translating a policy from this abstraction to the discrete network of interest. Translation is made possible through the use of safety-stocks that maintain feasibility of workload trajectories. This is a well-known approach in the queueing theory literature, and may be viewed as a generic approach to avoid deadlock in a discrete-event dynamical system. Simulation is used to evaluate a given policy, and to tune safety-stock levels. These simulations are accelerated through a variance reduction technique that incorporates stochastic approximation to tune the variance reduction. The search for appropriate safety-stock levels is coordinated through a cutting plane algorithm. Both the policy synthesis and the simulation acceleration rely heavily on the development of approximations to the value function through fluid model considerations.     

Experimental investigation and thermodynamic calculation of the Cu–In–Sb phase diagram

The phase diagram of the Cu–In–Sb ternary system is of importance in predicting the interface reaction between In-based solder materials and the Cu substrate.     

Numerical simulation of combined screw compressor–expander machines for use in high pressure refrigeration systems

Recent interest in natural refrigerants has created a new impetus for studies of CO₂ as a working fluid in vapour compression systems for refrigeration and air conditioning. Two major drawbacks to its use are the very high pressure differences required across the compressor and the large efficiency losses associated with the throttling process in the refrigeration cycle. It is shown how these disadvantages can be minimised by the use of a screw machine both to compress the gas and use the expansion process to recover power. Both these functions can be performed simultaneously, using only one pair of rotors, in a configuration that partially balances out the forces induced by the pressure difference and hence, reduces the bearing loads to an acceptable level. A further feature is the use of rotors, which seal on both contacting surfaces so that the same profile may be used for the expander and the compressor sections. This enables the rotors performing both these functions to be machined or ground in the same cutting operation and then separated by machining a parting slot in them. Computational Continuum Mechanics comprising both, fluid flow and structural analysis is used in this paper for the investigation of fluid-solid interaction in such machines.     

The interaction between calpastatin and RYR1 genes for some pork quality traits

This study was performed in order to investigate a relationship between polymorphism's of calapastatin gene (CAST) identified with HinfI, MspI and RsaI restriction endonucleases in pigs and meat quality characteristics and also interactions between CAST and RYR1 genes. Investigations were carried out on group of 89 fatteners being crosses of (Polish Large White×Polish Landrace)×(Hampshire×Pietrain). Some meat quality characteristics, glycolytic potential of LL muscle, yield of curing meat in cooking, the yield of loin in curing and smoking processes were determined. Statistically significant influence of RYR1 genotype (CC and CT) on investigated traits wasn't affirmed. A significant effect of CAST genotype on the value of several meat quality traits was noticed. Interactions between RYR1 and CAST genes were statistically significant for pH(45) value (CAST/RsaI×RYR1) and for drip loss (CAST/HinfI×RYR1). Obtained results showed that glycogen level in LL muscle in 45 min post mortem depends on CAST/MspI and CAST/RsaI genotypes while glycolytic potential depends on CAST/RsaI genotype. Genotyp AA at CAST/RsaI locus and AA genotype at CAST/HinfI locus stopped disclose of effect of RYR1 gene mutation for pH(45) in LD muscle and for drip loss respectively. Animals heterozygous in RYR1 locus (CT) being BB homozygotes at CAST/RsaI locus produced meat with highest pH(45) value (6,4) and dark meat colour. For technological properties of meat most interesting are double heterozygotes at the loci RYR1 and CAST/HinfI with significantly lowest (P?0.01) drip loss (4,04%).     

Statistical design of experiments of acid activation of smectite clay from Serbia and its bleaching capacity

BACKGROUND: Serbian smectite clay has been activated using a response surface method with central composite design. Because, among the criteria of an edible oil, colour is the most important factor in the commercial value of the oil, and since the colour is due to the presence of pigments such as β‐carotene in the crude oil, acid‐activated clay was used for decolourisation of soybean oil. RESULTS: The effects of five parameters, namely, temperature, time, acid strength, solid/liquid ratio and stirring speed, on the process of acid activation of the clay and its bleaching capacity were determined using a statistical model. The results indicated that all parameters were significant factors in the bleaching capacity of acid‐activated clay, and a quadratic polynomial equation for bleaching capacity was obtained by multiple regression analysis. The optimal bleaching capacity was estimated to be 96.61% for an experimental run under the following conditions: activation temperature 80 °C, HCl concentration 4.78 mol L^?1, stirring speed 450 rpm, solid/liquid ratio 1:4.5 and activation time 2.81 h. CONCLUSIONS: The central composite design, regression analysis and response surface method were effective in identifying the optimal conditions for bleaching capacity of acid‐activated smectite. Copyright © 2008 Society of Chemical Industry     

Flexible RollScann-design of one-tooth-roll-master and simulations for data acquisition

The recent improvements in the design and production of gears are not matched by the improvements in the development of measuring techniques and evaluation standards which can, in short time, give precise information about the quality of the produced gear. The inspection of gears with tooth flank modifications is still conducted by measuring of the profile and flank lines, pitch and concentricity. Furthermore topographical measurement on the coordinate measuring machine is an expensive and lasting process. This paper presents the development of a new, flexible gear-measuring machine called RollScan, which can measure the entire gear topography in a few minutes and can be introduced directly into the production line. For this, a machine with four axes and the control, a new one tooth roll master and evaluation software is designed, which makes the machine flexible and enables a variety of gear measurements without any special mechanical adjustments. The investigations described in this paper were sponsored by InnoNet from BMWi (16IN0276).     

Solution properties of poly(fluorostyrene-co-chlorostyrene) copolymers. I. Light scattering,differential refractometry and viscometry

The weight-average molecular weights (M?_w) of nominally random, unfractionated copolymers of ortho- and para-fluorostyrene and ortho- and para-chlorostyrene were determined by light scattering measurements in tetrahydro-furan, toluene, carbon tetrachloride and chloroform. It was shown that there is no significant variation in measured M?_w in the various solvents, a finding indicating that the copolymers are not compositionally heterogeneous. Intrinsic viscosity measurements in the same solvents established a consistent relationship between [n] and M?_w despite the differences in copolymer compositions. It was not possible to establish a similar relationship between the second virial coefficient A₂ and M?_w. It was concluded that measurements of the specific refractive index increment could be used for determining copolymer composition if the measurements were performed in thermodynamically poorer solvents. The results established for the Mark-Houwink constant α, intrinsic viscosity, and A₂ values indicated that these solvated copolymer molecules are in a less expanded conformation than are polystyrene molecules of similar molecular weights in a given solvent.     

Fuzzy logic based algorithms for maximum covering location problems

This paper concerns a class of maximum covering location problems in networks in uncertain environments. It is assumed that (a) relative weights of demand nodes are either deterministic or imprecise, described by linguistic expressions and (b) potential facility site locations are limited to network nodes. The concept of coverage is extended to include a degree of node coverage which means that the borders between the subset of covered demand nodes and the subset of uncovered demand nodes are inexact. The acceptable service distance/travelling times from a facility site to demand nodes are modelled by fuzzy sets. Three new algorithms for choosing the best facility locations are developed which assume that (1) demands at all nodes are equally important, (2) relative weights of demand at nodes are deterministic and (3) weights of demand at nodes are imprecise and described by linguistic terms, respectively. The algorithms are based on searching among potential facility nodes by applying comparison operations on discrete fuzzy sets. It is shown how to extend the proposed algorithms from one-site to multi-site covering problems. Illustrative examples of selecting locations for logistics centres in a distribution company are given.